The present invention relates to a new and distinct variety of Japanese pear tree which has a moderate vigor and an easily maintained moderate spur dvelopment, is resistant to black spot disease Alternaria alternata (Fries) Keissler Japanese pear pathotype, and is as productive as `Hosui`. The tree is cross-incompatible with `Kosui` and is assumed to have an S.sub.4 S.sub.5 genotype, and has brown young leaves and white large flowers which have a pale red color at the pit at fat bud and bloom middle to late in the season and at almost the same time as `Nijisseiki`. The tree can produce an oblate-shaped fruit which matures early in the season, earlier than `Nijisseiki`, and has a normal keeping quality. The fruit has a large size which is larger than that of `Nijisseiki`, a yellowish green skin which is partly covered with russet when cultivated without bagging, and a white flesh which is soft, crisp and very juicy, with a high sweetness, a low acidity, no astringency, and a slight aromatic flavor, giving an excellent dessert quality.
The characteristics of cultivars of Japanese pear trees mentioned for comparison are as follows.
`Nijisseiki`; Representative cultivar producing a fruit with yellowish green skin. Middle ripening. The tree is very susceptible to black spot disease. The appearance of the fruit is aesthetically enhanced by bagging.
`Hosui`; Excellent cultivar known as a "Sansui" (i.e., three cultivars having a Japanese name ending in "sui", respectively, i.e., `Kosui`, `Shinsui`, and `Hosui`). Middle ripening. Bearing a fruit with brown russeted skin.
`Chojuro`; Former representative cultivar producing a fruit with brown russeted skin. Middle ripening. The production of this fruit has been recently reduced in Japan.
`Kozo`; The fruit has a brown russeted skin, and produces a characteristic aroma flavor at full maturation. The tree is little cultivated now in Japan.
`Wase-Kozo`; Bud mutant of `Kozo`. Early ripening. Bearing a fruit with brown russeted skin. This cultivar is little cultivated now in Japan.
The symbol "S.sub.x S.sub.y " (wherein x and y are an integer, respectively) used in this specification means the type (genotype) of multiple alleles which controls the incompatibility of plants and is inherent to each cultivar. The relationship between style and pollen, and whether it would be fertile or sterile, depend on the genotype of each. That is, when a style and a pollen both have a same genotype, the relationship becomes sterile. For example, `Nijisseiki` having an S.sub.2 S.sub.4 genotype is cross-incompatible with `Kikusui` having the same genotype S.sub.2 S.sub.4.
All places and addresses mentioned in this specification are in Japan, unless otherwise specified.
Our breeding program was aimed at obtaining a new early variety of Japanese pear tree producing, first, a fruit having skin which is at early maturity of the yellowish green color identified in the Munsel.RTM. Book of Color as follows:
Hue symbol: 2.5 gy PA1 Chroma: 6 PA1 Value: 9, PA1 Hue symbol: 10 y PA1 Chroma: 6 PA1 Value: 9, PA1 Hue symbol: 2.5 gy PA1 Chroma: 6 PA1 Value: 9, PA1 Hue symbol: 10 y PA1 Chroma: 6 PA1 Value: 9, PA1 Hue symbol: 2.5 gy PA1 Chroma: 6 PA1 Value: 9, PA1 Hue symbol: 10 y PA1 Chroma: 6 PA1 Value: 9,
and which is at full maturity of the yellow color identified in the Munsel.RTM. Book of Color as follows:
and an excellent quality flesh for dessert; second, resistant to black spot disease; and third, easy to grow and productive.
The new variety of Japanese pear tree was a cross-seedling which originated from a crossing of `Kikusui (.female.)`.times.`Kosui (.male.)` in 1963 at the Horticultural Research Station of the Ministry of Agriculture and Forestry, residing at Hiratsuka-shi, Kanagawa-ken, Japan, and was top-worked onto `Chojuro` as an interstock and given the number `48-108`, in 1966. The tree bore some fruit for the first time in 1969.
The tree was selected in 1971 and subjected to local adaptability tests from 1972 at the experimental stations in main pear growing regions of Japan, e.g., in Tottori-ken, Saitama-ken Ibaraki-ken, Chiba-ken, Miyagi-ken, Fukushima-ken and the like, as the strain number `Hiratsuka No. 28`. As a result, this new variety of Japanese pear tree according to this invention was judged to be resistant to black spot disease and to produce an excellent quality fruit which is large, has a skin which is at early maturity of the yellowish green color identified in the Munsel.RTM. Book of Color as follows:
and which is at full maturity of the yellow color identified in the Munsel.RTM. Book of Color as follows:
and can be harvested earlier than `Nijisseiki`. This new variety of Japanese pear tree was named `Syuugyoku` in June, 1986.
The pedigree of `Syuugyoku` is shown in FIG. 1.
`Kikusui`, used as a female parent in the breeding of `Syuugyoku`, was selected from seedlings which originated from a crossing of `Taihaku`.times.`Nijisseiki` for the purpose of obtaining a variety of Japanese pear tree resistant to black spot disease by Akio Kikuchi at the farm of the former Tokyo Prefectural Horticultural School. The tree was grown and tested at the former Ninoniya Horticulture Division of the Kanagawa Prefectural Agricultural Experiment Station. As a result, the tree was judged to be superior, and named `Kikusui` in 1927. The main characteristics of `Kikushi` are as follows.
Tree: Having a good bearing character. PA0 Branches: PA0 Leaves: PA0 Flowers: PA0 Fruit: PA0 Resistance to pests and diseases: Resistant to black spot disease and scab. PA0 Tree: PA0 Branches: PA0 Leaves: PA0 Flowers: PA0 Fruit: PA0 Resistance to pests and diseases: Resistant to black spot disease and susceptible to canker. The resistance to scab is weaker than that of `Nijisseiki`, but stronger than that of `Chojuro`.
Vigor.--Strong. PA2 Spur.--Bearing heavily. PA2 Predominance of axillary flower bud.--Many. PA2 Production.--Highly productive. PA2 Cross-incompatibility.--Cross-incompatible with, e.g., `Nijisseiki` and assumed to have an S.sub.2 S.sub.4 genotype. PA2 Thickness.--Medium. PA2 Color of young leaves.--Grayish white. PA2 Size.--Large. PA2 Color.--White. PA2 Form of petals.--Double or semi-double. PA2 Pollen.--Abundant. PA2 Flowering time.--Almost the same time as `Nijisseiki`, e.g., mid-to-late April in Kanto district, Japan. PA2 Physiological fruit drop.--Somewhat much during the harvesting period. PA2 Size.--Medium, about 300 g. PA2 Shape.--Oblate with a very wide and shallow stalk cavity and a slightly wide and deep eye basin. PA2 Color of skin.--Yellowish green. PA2 Size of dot.--Slightly large. PA2 Thick peduncle.--Occurring easily. PA2 Flesh.--Soft and juicy. PA2 Taste.--Having a high sweetness, a slight acidity, and an excellent dessert quality that is better than `Nijisseiki`. PA2 Maturity.--Ripening at almost the same time as or a little earlier than `Nijisseiki`, e.g., mid-to-late September in the Kanto district, Japan. PA2 Keeping quality.--Somewhat poor. PA2 Vigor.--Slightly strong. PA2 Spur.--Insufficient bearing, and difficult to maintain. PA2 Predominance of axillary flower bud.--Few. PA2 Production.--Medium. PA2 Cross-incompativility.--Cross-incompatible with, e.g., `Taihaku`, and assumed to have an S.sub.4 S.sub.5 genotype. PA2 Thickness.--Slightly slender. PA2 Color of young leaves.--Reddish brown. PA2 Size.--Large. PA2 Color.--White, but pale red in fat bud. PA2 Pollen.--Abundant. PA2 Flowering time.--Almost the same time as or two to three days later than `Chojuro`, e.g., mid-to-late April in Kanto district, Japan. PA2 Size.--Medium, 250-300 g. PA2 Shape.--Slightly oblate with a wide stalk cavity and a wide and deep eye basin. PA2 Color of skin.--Greenish brown. PA2 Skin.--Usually covered with brown spot. PA2 Thick peduncle.--None. PA2 Color of flesh.--White. PA2 Flesh.--Fine, juicy, softer than `Nijisseiki`, and having a firmmess of 3.8 lbs. in Magnessteller's hardness meter index. PA2 Taste.--Having a high sweetness (the sugar content of the fruit juice is 12%) and little acidity. Sometimes producing a characteristic aromatic flavor of `Kozo` or `Wase-Kozo` when the fruit is over-ripe. PA2 Maturity.--Ripening about ten days earlier than `Chojuro`, e.g., in the end of August to early September in the Kanto district, Japan. PA2 Keeping quality.--Moderate, but good as an early-maturing cultivar.
`Kosui`, used as a male parent in the breeding of `Syuugyoku`, was a seedling of a crossing of `Kikusui`.times.`Wase-Kozo` in 1941 at the Horticultural Research Station of the Ministry of Agriculture and Forestry, residing at Okitsu-machi, Ihara-gun, Shizuoka-ken, Japan, and given the number `Wi-26`. The tree bore fruit for the first time in 1947. The tree was selected in 1949 and subjected to local adaptability tests at the experimental stations in main pear growing regions of Japan. As a result, the tree was judged to be a superior cultivar that produces fruit with brown russeted skin, and was named `Kosui` in 1959. The main characteristics of `Kosui` are as follows.
We asexually reproduced this new and distinct variety of Japanese pear tree `Syuugyoku`, by grafting, at the Fruit Tree Research Station, Ministry of Agriculture, Forestry and Fisheries, residing at 2-1 Fujimoto, Yatabe-machi, Tsukuba-gun, Ibaraki-ken, Japan, and confirmed the homogeneity and stability of `Syuugyoku` according to this invention.
An application for this new variety of Japanese pear tree `Syuugyoku` under the Seeds and Seedling Law of Japan was filed on Mar. 31, 1986.